A new modular magnetorheological fluid valve for large-scale seismic applications

Abstract

This study presents a modular, large-scale, magneto-rheological (MRF) by-pass valve to be used in seismic damper retrofits for energy mitigation. The by-pass valve is designed, constructed and tested. The MR valve can be used to retrofit a commercial passive seismic damper as a semi-active device. The performance of the MRF valve was characterized by means of quasi-static characterizations. A new MR fluid is also developed for the seismic by-pass MRF damper application. This MR fluid has low off-state viscosity and high field-dependent yield strength. The field-dependent rheology of the MR fluid is evaluated with a MR shear rheometer. In addition, a theoretical model is developed taking into account geometric dimensions, fluid properties and applied magnetic field strength. Three-dimensional electromagnetic finite element analysis is used to determine and maximize the magnetic field strength inside the by-pass MRF valving region. Both experimental and theoretical results show that the modular large-scale by-pass MRF damper can generate sufficient dynamic force range which meets the high-force requirements of large-scale structures subjected to seismic or other significant hazards.